1. Field of the Invention
The invention relates to a method for treating lung disease, and more particularly, the invention relates to a method of increasing gas exchanging of a lung by stiffening an airway of the lung.
2. Brief Description of the Related Art
The lungs deliver oxygen to the body and remove carbon dioxide. Healthy lung tissue includes a multitude of air passageways which lead to respiratory bronchiole within the lung. These airways eventually lead to small sacs called alveoli, where the oxygen and carbon dioxide are exchanged through the ultra-thin walls of the alveoli. This occurs deep within the lungs, in an area which is accessed by a network of airways, consisting of a series of branching tubes which become narrower, shorter, and more numerous as they penetrate deeper into the lungs. As shown in FIG. 1, tiny air sacks called alveoli 1 surround both alveolar ducts 2 and respiratory bronchiole 3 throughout the lung. The alveoli 1 are small, polyhedral recesses composed of a fibrillated connective tissue and surrounded by a few involuntary muscular and elastic fibers. These alveoli 1 inflate and deflate with air when we breath. The alveoli are generally grouped together in a tightly packed configuration called an alveolar sac. The thin walls of the alveoli 1 perform gas exchange as we inhale and exhale.
During inhalation, as the diaphragm contracts and the ribs are raised, a vacuum is created in the chest, and air is drawn into the lungs. As the diaphragm relaxes, normal lungs act like a stretched balloon and rebound to the normal relaxed state, forcing air out of the lungs. The elasticity of the lungs is maintained by the supportive structure of the alveoli. This network of connective tissue provides strength to the airway walls, as well as elasticity to the lungs, both of which contribute to the lung's ability to function effectively.
Patients with pulmonary disease, such as chronic bronchitis, and emphysema have reduced lung capacity and efficiency, typically due to the breakdown of lung tissue.
In cases of severe chronic pulmonary disease, such as emphysema, lung tissue is destroyed, reducing the strength of the airways. This reduction in strength of the airway walls allows the walls to become “floppy” thereby losing their ability to remain open during exhalation. In the lungs of an emphysema patient, illustrated in FIG. 2, the walls between adjacent alveoli within the alveolar sac deteriorate. This wall deterioration is accelerated by the chemicals in smoke which affect the production of mucus in the lungs. Although the break down of the walls of the alveoli in the lungs occurs over time even in a healthy patient, this deterioration is greatly accelerated in a smoker causing the smoker's lungs to have multiple large spaces 4 with few connecting walls in the place of the much smaller and more dense alveoli spaces 1 in healthy lung tissue.
A cross section of a diseased emphysematous lung will look like Swiss cheese due to the deterioration of the alveoli walls which leaves large spaces in the tissue. In contrast, healthy lung tissue when seen in cross section has no noticeable holes because of the small size of the alveoli. When many of the walls of the alveoli 1 have deteriorated as shown in FIG. 2, the lung has larger open spaces 4 and a larger overall volume, but has less wall tissue to achieve gas exchange.
In this diseased state, the patient suffers from the inability to get the air out of their lungs due to the collapse of the airways during exhalation. Heavily diseased areas of the lung become overinflated. Within the confines of the chest cavity, this overinflation restricts the in-flow of fresh air and the proper function of healthier tissue, resulting in significant breathlessness. Thus, the emphysema patient must take in a greater volume of air to achieve the same amount of gas exchange. When severe emphysema patients take in as much air as their chest cavity can accommodate, they still have insufficient gas exchange because their chest is full of non-functional air filling large cavities in the lungs. Emphysema patients will often look barrel-chested and their shoulders will elevate as they strain to make room for their overinflated lungs to work.
A wide variety of drugs are available for treating the symptoms of pulmonary disease, but none are curative. Chronic bronchitis and emphysema are typically treated with antibiotics and bronchodilators. Unfortunately, a large number of patients are not responsive to these medications or become non-responsive after prolonged periods of treatment.
In severe emphysema cases, lung volume reduction surgery (LVRS) is performed to improve lung efficiency of the patient and allow the patient to regain mobility. In lung volume reduction surgery, a more diseased portion of an emphysematous lung having a large amount of alveolar wall deterioration is surgically removed. LVRS is performed by opening the chest cavity, retracting the ribs, stapling off, and removing the more diseased portion of the lung. This allows the remaining healthier lung tissue to inflate more fully and take greater advantage of the body's ability to inhale and exhale. Because there is more air and more gas exchange in the healthier portion of the lung, lung efficiency is improved.
Lung volume reduction surgery is an extremely invasive procedure requiring the surgical opening of the chest cavity and removal of lung tissue. This surgery has substantial risks of serious post-operative complications, such as pneumothorax, and requires an extended convalescence.
Accordingly, it is desirable to improve air exchange for patients having chronic obstructive pulmonary diseases, such as chronic bronchitis and emphysema. It is especially desirable to achieve improved air exchange of emphysema patients without invasive open chest surgery and the associated complications.